Manufacture of resinous products derived from acrylic acid



Patented Mu.'2s,"1944 MANUFACTURE OF RESINOUS PRODUCTS DERIVED FROM ACRYLIC ACID Thomas Sefton Ireland, Penketh, Warrington,

England, assignor to Imperial Chemical Industries Limited, a corporation or Great Britain No Drawing. Application February 28, 1940, Se-

il'gizlgNo. 321,352. In Great Britain March 9,

11 Claims.

This invention relates to improvements in the manufacture of resinous products obtained from alpha-haloacrylic acid esters.

It has been proposed in copending United States patent application Serial No. 270,900, filed April 29, 1939, now U. S. Patent No. 2,286,264, to prepare moulding compositions, comprising interpolymers of alpha-chloroorylic esters with other unsaturated organic compounds, together, if desired, with plasticizers, softeners or fillers. In many cases the appearance of polymers of alphachloroacrylic acid and its esters is marred by a yellowish coloration, sometimes apparent immediately on polymerisation, while in other cases only after a lapse of time orwhen the materials are heated. The formation of this yellow colour is believed to be due to the presence of autooxidation products of the monomer. In copending U. S. Patent No. 2,314,443, issued March 23, 1943, it has been proposed 'to bring about considerable diminution in the extent of the coloration by subjecting the monomer to-a treatment which will free it' from autoxidationwproducts, e. g.,

by distillation in the substantial absence of atmospheric oxygen, preferably after-washing with an aqueous reducing agent, or by; treatment with a reducing agent or a compound having a labile oxygen atom, and simultaneously or subsequent- Esters which may be treated according to my invention include, for example, the methyl and ethyl esters and the propyl esters of alpha-chloroacrylic acid and of alpha-bromoacrylic acid, and the invention may be usefully applied to alpha-chloroacrylic acid esters which have been treated according to U. 8. Patent No. 2,314,443, issued March 23, 1943. The inhibition of color production is evidenced not only during the steps of polymerising the monomeric body, but also in the improved resistance of the resin towards development of colour on prolongedheating.

' Examples of stabilizer for the polymeric esters which may be usediip my invention include glycoland glycerol, 'and smtable ester andether derivatives-are the isomeric formsof monoacetin,

I diacetin,; (monobutyrin, .glyc'eryl monophenyl etherlandg'glyceryldiphenyl ,ether. While" the above compounds are allsuificiently soluble for usein my invention, othercompounds, 'e. 'g.,'

, the higher polyhydric alcohols such as the hexto develop yellow coloration. It isa'i'urther ob ject of the invention to prepare resinous prod ucts from alpha-chloroacrylic acid esters which have an even smalleritendency to develop yellow coloration. A further object of the invention is to prepare noveiresinous compositions from alpha-haloacrylic acid esters having a-high stability againstcoloration on heating; It he still further object of the'inventiontoprepare novel resinous compositions from alpha-chloroacrylic esters having high stability against coloration on heating. Other objects will be apparent hereinaiter; According to the present invention these ob.- iects are achieved by incorporating with a polymerisable ester of .an alpha-haloacrylic acid which is substantially vfree from autoxidation products, or with a composition comprising such an ester, a stabiliser for the polymeric ester as,

oses, have but 'a vanishingly small solubility in at least-the majority of alpha-haloacrylic acid esters, and in such cases are not suitable for use in my invention. In general a small proportion, e. g., 0.1 per cent to 5.0 percent by weight.

of the stabilizer is a suitable amount to incorporate in the polymerisable ester. 7

The incorporation of the stabiliser is conveniently effected by dissolving it in the monomeric'body shortly before polymerisation, or in the case of monomers treated by such processes asthose forming the subject of copending U. S. Patent No. 2,314,443, issued March 23, 1943, immediately after such treatments have been carried out. The compounds may also be incorporated "with partially polymerised alpha-haloacrylic acid. esters which are still in a liquid condition. However, in such cases some colour may have been generated during the partial polymerisation, and for this reason we have found it better to incorporate the stabiliser in the monomeric body.

The polymerisation oi' the ester to the resinous condition is preferably eilected by heating in the present of a peroxide polymerisation catalyst such as benzoyl peroxide or succinyl monoperacid, and it may be carried out so as to produce articles directly; alternatively, for example, the monomer may be polymerised in globular suspension to produce a granular polymer, or emulsions of the monomer may be polymerised giving emulsions of the polymer. It is also possible to effect the polymerisation by the action of actinic radiation, but such radiation also promotes antoxidation, and thus where this method is to be employed, oxygen or oxygen-containing gases, e. g., air, should be excluded during the polymerisation.

The invention may also be applied to the manui'acture of resinous products by interpolymerising an alpha-haloacrylic acid ester, e. g., an alpha-chloroacrylic acid ester, with a second polymerisable compound, such as a vinyl compound, or with a compound which while not itself polymerisable forms interpolymers with alpha-haloacrylic compounds, as, for example, with a crotonic acid ester or an ester of beta-methyl allyl alcohol. Thus a monomeric alpha-chloroacrylic acid ester treated with a stabilizer for the polymeric ester according to the invention, may be mixed with a second constituent and the interpolymer formed by subjecting the mixture to heat, suitably in the presence of a polymerisation catalyst. Subsequent generation of colour in the interpolymer is accordingly diminished.

"The following examples illustrate but do not limit my invention, all parts being by weight:-

Example I were mixed with 0.5 per cent of monoacetin and monobutyrin resspectively: two further portions also containing each 0025 per cent of benzoyl peroxide as a polymerisation catalyst were mixed with 0.2 per cent of ethylene glycol and glycerol respectively. The portions were then polymerised by heating at C. for 20 hours. Cylindrical specimens of ,each sample were prepared each '1 cm". long and having polished ends, and the colour of each cylinder as viewed along its axis was determined by a Lovibond tintometer after heating at 100-110 C. for various times. The colour so measured is given in the following table, expressed as total Lovibond units. In each case the total is composed of red and yellow values, the yellow predominating in each case. For comparison there is given in the table colour of a sample obtained and treated in pre- I cisely the same way except for the incorporation of a colour inhibitor.

Reagent Colour None l. 0 Glyoeryl monophenyl other 96%) l. 2 Glyoeryl diphenyl other (0.6 0.0

Certain variations from the description set forth in the foregoing will be evident to those skilled in the art. I intend therefore to be bound onlyin accordance with the following claims. j

I claim: 1. Process for the manufacture ofpolymerised alpha-haloacrylic acid ester compositions which comprises incorporating with a composition comprising a polymerisable ester of a saturated alcohol with an alpha-haloacrylic acid substantially free from autoxidation products, a stabilizer for the polymeric alpha-haloacrylic ester consisting of a monomeric compound soluble to the colour of a sample obtained and treated in the same way except for theincorporation of a colour inhibitor.

Portions of a diflerent sample of methyl alpha,- chloroacrylate substantially free from autoxidation products of the monomer but containing each 0.025 per cent of benzoy peroxide as polymerisation catalyst, were mixed with 0.5 per cent the extent of at least 0.1 per cent in the monomeric ester and selected from the class consisting of polyhydric alcohols wherein the hydroxyls are attached to a saturated aliphatic hydrocarbon radical, partial esters thereof with short chain saturated aliphatic monocarboxylic acids and partial ethers thereof and subsequently polymerising the composition.

2. Process according to claim 1 in which the alpha-haloacrylic acid ester is an ester of alphachloroacrylic acid.

3. Process according to claim 1 in which the polyhydric alcohol of the stabilizer is g ycerol.

4. Process for the manufacture of polymerised alpha-haloacrylic acid ester compositions which comprises incorporating with a polymerisable ester of a saturated alcohol with an alpha-helm acrylic acid substantially free from autoxidation products a stabilizer for the polymeric alphahaloacrylic ester consisting of a compound sol- ,uble to the extent of at least 0.1'per cent in the; monomeric ester and selected from the class con-; sisting of polyhydric alcohols wherein the hydroxyls are attached to a saturated aliphatic hydrocarbon radical, partial esters thereof with short chain saturated aliphatic monocarboxylic acids and partial ethers thereof, and subsequently polymerising the composition,

5. Process according to claim 4 in. which the alpha-haloacrylic acid ester is an ester of alphachloroacrylic acid.

6. Process according to claim 4 in which the stabilizer is present in amounts between 0.1%

and 5% by weight of the alpha-haloacrylic ester.

7. Process for the manufacture of polymerised alpha-haloacrylic acid ester compositions which comprises incorporating with a composition comprising a polymerisable ester of a'saturated alcohol with an alpha-haloacrylic acid sub stantially free from autoxidation products a stabiliaer for the polymeric alpha-haloacrylic ester consisting of a monomeric compound soluble to bon radical, partial esters thereof with short 6 chain saturated aliphatic monocarboxylic acids and partial ethers thereof, and subsequently polymerising the composition by heating in the presence of a peroxide polymerisation catalyst.

8. Process according to claim 7 in which the 10 polymerisation catalyst is benzoyl peroxide.

9. Process for the manufacture of polymerised alpha-haloacrylic acid ester compositions which comprises incorporating with a composition comprising a. polymerizable ester of a saturated alcohol with an alpha-haloacrylic acid substantially free from autoxidation products a partial ester 01 glycerol with a short chain saturated aliphatic monocarboxylic acid as a stabilizer for the polymeric alpha-haloacrylic acid ester, and subsequently polymerizing the composition.

10. Process of claim 9 wherein the polymerizable ester is an alpha chloroacrylic acid ester and the stabilizer is monoacetin. I

11. Process of claim 9 wherein the polymerizable ester is methyl alpha-chloroacrylate and the stabilizer is monoacetin.

THOMAS SEFTON l- 

